In many commercial applications, battery energy performance, safety, and life usage are critical. Lithium-ion batteries are increasingly being used to meet the energy and power demands of consumer electronics and portable electronics as well as vehicles such as automobiles, electric bikes, airplanes, and satellites.
In conventional two-dimensional design in lithium-ion batteries, the electrodes are casted onto metal foil current collectors. Due to the poor electronic conductivity of the electrodes, slow ion transport, and high tortuosity of electrodes, layer thicknesses are limited to a range of 50-100 μm. Reducing the layer thickness to minimize the cell resistances comes at the price of reduced energy density and higher costs, as there are more inactive components (e.g. current collectors and separators) per unit mass of active materials. An ultra-thick electrode for battery is a practical approach to improve the energy density while reducing the costs. However, increasing the thickness of a battery electrode without compromising cell electrochemical performance such as power density and cycling stability is very challenging. As the electrode thickness increases, conventional electrodes suffer from resistance rise associated with both electronic and ionic transports. Higher resistance often translates to higher voltage loss for the cell.
A “convection battery” or “convection cell” forces flow of electrolyte through the cathode, anode, and the separator between them. Electrolytes are convected (transported by flow) by a mechanical pump through porous electrodes to decrease diffusion overpotential losses and make the potential more uniform throughout the electrode. One goal is to increase ion fluxes to realize the benefit of thicker electrodes, lower cost batteries, and reduced charge times. Electrolyte flow is used to reduce mass transfer overpotentials or to eliminate dendrite modes of failure. In particular, flow in a convection battery can reduce concentration overpotentials by 99% or more (see Gordon and Suppes, “Convection battery-modeling, insight, and review,” AIChE Journal, Volume 59, Issue 8, pages 2833-2842, August 2013).
Generally, a convection battery utilizes principles of chemical engineering that are common in large chemical plants, such as heat integration and interaction with mass transport, within a battery configuration. In view of the ability of a convection battery to overcome both bulk diffusion and liquid-phase conductivity limitations, convection batteries have genuine potential to redefine the performance of batteries, such as lithium-ion batteries.
However, improved battery structures and frameworks are sought in order to realize this theoretical potential of convection batteries. Three-dimensional electrode and current-collector designs are needed that optimize both ion transport and electron transport. In addition, convenient methods to fabricate such structural battery designs are desired in the art.